Doctors have made leaps and bounds with curing patients of HIV, but today, an equally-groundbreaking study has proven that emerging preventative treatments are even more effective than previously thought.

The study, which was published in The Lancet today, concerns pre-exposure prophylaxis (or PrEP), a newish preventative treatment in which at-risk patients take a daily pill to prevent infection. PrEP can also take the form of a gel used to prevent transmission between an infected mother and her child, at birth. It’s been around for a few years, and other studies have suggested that it’s hugely helpful.

So what makes today’s report so different? Well, according to The New York Times, scientists have long assumed that PrEP wouldn’t work for drug addicts, simply because of the speed at which HIV shot through the population in the 1980s. Instead, most PrEP studies focused on preventing transmission between sexual partners, or between mothers and their children, assuming that the treatment wouldn't be as helpful for drug users. Turns out, that’s not the case at all. The study tested PrEP amongst 2,400 drug addicts in Thailand, where shared needles are a hugely common way to transmit HIV. Participants were given a daily pill—and when they were tested for transmission, those taking the PrEP were a staggering 74 percent less likely to be infected.

Now that they know PrEP definitively works for such an at-risk population, HIV and AIDS researchers are facing another huge challenge: figuring out how to get addicts—who are difficult to treat, as well as study—to commit to the treatment. In fact, one Canadian researcher quoted by the NYT pointed out that the logistics and cost of distributing PrEP meds might actually outweigh the benefits, along with overshadowing proven outreach programs like clean needles, methadone, and test-and-treat.

Still, this study is important news—in the words of the same researcher, “a new piece to the puzzle”—that puts us one step further down the road to eradicating HIV. [The New York Times]